A detailed molecular understanding of the function of conductive channels is an important unresolved problem in the electrophysiology of excitable cell membranes such as those of heart and nerve. This study is designed to elucidate the basic relationships between the structure and the function of conductive channels. It proposes a systematic study of the permeability as well as the chemical and electrical control (gating) of transmembrane channels formed in lipid bilayer membranes by simple synthetic peptides of known chemical and conformational structures. It is reasoned that a quantitative study of conductive channels of well defined structures constitutes one of the more promising approaches towards a global understanding of the rules that govern the physiological function of transmembrane channels. Initial phases of the research will explore the structure-function relationship for two classes of compounds. One class is comprised of appropriately designed derivatives of gramicidin A, for example N-acetyl or BOC-gramicidins. The other class is comprised of peptides analogous to HCO-(L-Ala-L-Ala-Gly)5-OMe which forms selective, electrically gatable channels. Two essential aspects of the channel structure-function relationship will be examined. These are the effects of channel molecular structure on 1) channel permeability and 2) kinetics of channel formation and breakdown. Emphasis will be placed on the electrical and chemical control of these processes. A quantitative molecular understanding of the structure-function relationship for transmembrane channels whose structures approximate with increasing fidelity those of excitable cell membranes, is expected to reveal not only the molecular role of membrane components but also some of the basic mechanisms by which pharmacological agents (e.g., channel blockers, anaesthetics) alter membrane physiological function.